The ncurses library routines give the user a terminal-independent method of updating character screens with reasonable optimization. This implementation is new curses (ncurses) and is the approved replacement for 4.4BSD classic curses, which has been discontinued.
The ncurses routines emulate the curses(3X) library of System V Release 4 UNIX, and the XPG4 curses standard (XSI curses) but the ncurses library is freely redistributable in source form. Differences from the SVr4 curses are summarized under the EXTENSIONS and BUGS sections below and described in detail in the EXTENSIONS and BUGS sections of individual man pages.
A program using these routines must be linked with the -lncurses option, or (if it has been generated) with the debugging library -lncurses_g. (Your system integrator may also have installed these libraries under the names -lcurses and -lcurses_g.) The ncurses_g library generates trace logs (in a file called trace in the current directory) that describe curses actions.
The ncurses package supports: overall screen, window and pad manipulation; output to windows and pads; reading terminal input; control over terminal and curses input and output options; environment query routines; color manipulation; use of soft label keys; terminfo capabilities; and access to low-level terminal-manipulation routines.
To initialize the routines, the routine initscr or newterm must be called before any of the other routines that deal with windows and screens are used. The routine endwin must be called before exiting. To get character-at-a-time input without echoing (most interactive, screen oriented programs want this), the following sequence should be used:
initscr(); cbreak(); noecho();
Most programs would additionally use the sequence:
Before a curses program is run, the tab stops of the terminal should be set and its initialization strings, if defined, must be output. This can be done by executing the tput init command after the shell environment variable TERM has been exported. tset(1) is usually responsible for doing this. [See terminfo(5) for further details.]
The ncurses library permits manipulation of data structures, called windows, which can be thought of as two-dimensional arrays of characters representing all or part of a CRT screen. A default window called stdscr, which is the size of the terminal screen, is supplied. Others may be created with newwin.
Note that curses does not handle overlapping windows, thats done by the panel(3X) library. This means that you can either use stdscr or divide the screen into tiled windows and not using stdscr at all. Mixing the two will result in unpredictable, and undesired, effects.
Windows are referred to by variables declared as WINDOW *. These data structures are manipulated with routines described here and elsewhere in the ncurses manual pages. Among which the most basic routines are move and addch. More general versions of these routines are included with names beginning with w, allowing the user to specify a window. The routines not beginning with w affect stdscr.)
After using routines to manipulate a window, refresh is called, telling curses to make the users CRT screen look like stdscr. The characters in a window are actually of type chtype, (character and attribute data) so that other information about the character may also be stored with each character.
Special windows called pads may also be manipulated. These are windows which are not constrained to the size of the screen and whose contents need not be completely displayed. See curs_pad(3X) for more information.
In addition to drawing characters on the screen, video attributes and colors may be supported, causing the characters to show up in such modes as underlined, in reverse video, or in color on terminals that support such display enhancements. Line drawing characters may be specified to be output. On input, curses is also able to translate arrow and function keys that transmit escape sequences into single values. The video attributes, line drawing characters, and input values use names, defined in <curses.h>, such as A_REVERSE, ACS_HLINE, and KEY_LEFT.
If the environment variables LINES and COLUMNS are set, or if the program is executing in a window environment, line and column information in the environment will override information read by terminfo. This would effect a program running in an AT&T 630 layer, for example, where the size of a screen is changeable (see ENVIRONMENT).
If the environment variable TERMINFO is defined, any program using curses checks for a local terminal definition before checking in the standard place. For example, if TERM is set to att4424, then the compiled terminal definition is found in
(The a is copied from the first letter of att4424 to avoid creation of huge directories.) However, if TERMINFO is set to $HOME/myterms, curses first checks
and if that fails, it then checks
This is useful for developing experimental definitions or when write permission in /usr/share/misc/terminfo is not available.
The integer variables LINES and COLS are defined in <curses.h> and will be filled in by initscr with the size of the screen. The constants TRUE and FALSE have the values 1 and 0, respectively.
The curses routines also define the WINDOW * variable curscr which is used for certain low-level operations like clearing and redrawing a screen containing garbage. The curscr can be used in only a few routines.
Routine and Argument Names
Many curses routines have two or more versions. The routines prefixed with w require a window argument. The routines prefixed with p require a pad argument. Those without a prefix generally use stdscr.
The routines prefixed with mv require a y and x coordinate to move to before performing the appropriate action. The mv routines imply a call to move before the call to the other routine. The coordinate y always refers to the row (of the window), and x always refers to the column. The upper left-hand corner is always (0,0), not (1,1).
The routines prefixed with mvw take both a window argument and x and y coordinates. The window argument is always specified before the coordinates.
In each case, win is the window affected, and pad is the pad affected; win and pad are always pointers to type WINDOW.
Option setting routines require a Boolean flag bf with the value TRUE or FALSE; bf is always of type bool. The variables ch and attrs below are always of type chtype. The types WINDOW, SCREEN, bool, and chtype are defined in <curses.h>. The type TERMINAL is defined in <term.h>. All other arguments are integers.
Routine Name Index
The following table lists each curses routine and the name of the manual page on which it is described. Routines flagged with * are ncurses-specific, not described by XPG4 or present in SVr4.